Compiling with 'g++ -ggdb' confuses both gdb-6.5 and gdb-6.6 into thinking they've got corrupted stacks. My programs all seem to execute properly, both alone and inside gdb -- it's just hard to debug anything. Using 'g++ -g' instead seems to work fine.

Consider 'g++ -ggdb foo.cpp' with the following code snippet:

void foo() {
  int i;
  i=1;
}

int main() {
  foo();
  return 0;
}

Below is the gdb output as I step through the resulting executable. 

Current directory is c:/cygwin/home/johnsory/experiments/
GNU gdb 6.6
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This GDB was configured as "i686-pc-cygwin"...
(gdb) start
Breakpoint 1 at 0x401071: file foo.cpp, line 6.
Starting program: /home/johnsory/experiments/a.exe 
Loaded symbols for /cygdrive/c/WINDOWS/system32/ntdll.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/kernel32.dll
Loaded symbols for /usr/bin/cygwin1.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/advapi32.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/rpcrt4.dll
main () at foo.cpp:6
(gdb) step
(gdb) bt
#0  main () at foo.cpp:7
(gdb) step
foo () at foo.cpp:1
(gdb) bt
#0  foo () at foo.cpp:1
#1  0x00401050 in mainCRTStartup ()
(gdb) step
(gdb) bt
#0  foo () at foo.cpp:3
#1  0x00401056 in foo () at foo.cpp:1
#2  0x00401056 in foo () at foo.cpp:1
#3  0x00401056 in foo () at foo.cpp:1
#4  0x00401056 in foo () at foo.cpp:1
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
(gdb) step
(gdb) bt
#0  foo () at foo.cpp:4
#1  0x0040105d in foo () at foo.cpp:3
#2  0x0040105d in foo () at foo.cpp:3
#3  0x0040105d in foo () at foo.cpp:3
#4  0x0040105d in foo () at foo.cpp:3
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
(gdb) step
main () at foo.cpp:8
(gdb) bt
#0  main () at foo.cpp:8
(gdb) step
(gdb) bt
#0  main () at foo.cpp:9
(gdb) step
0x61006198 in dll_crt0_1 () from /usr/bin/cygwin1.dll
(gdb) bt
#0  0x61006198 in dll_crt0_1 () from /usr/bin/cygwin1.dll
#1  0x61004416 in _cygtls::call2 () from /usr/bin/cygwin1.dll
#2  0x00000000 in ?? ()
(gdb) step
Single stepping until exit from function _Z10dll_crt0_1Pv, 
which has no line number information.

Program exited normally.
(gdb)